J M Warman et al 2009 Phys. Med. Biol. 54 3185 doi:10.1088/0031-9155/54/10/015
J M Warman, M P de Haas and L H Luthjens
Show affiliationsA method of radiation dosimetry is described which is based on the radiation-induced initiation of polymerization of a bulk monomer (e.g. methyl methacrylate) containing a small concentration (about 100 ppm) of a compound which is non-fluorescent but which becomes highly fluorescent when it is incorporated into a growing polymer chain of the bulk monomer. We call the overall process 'radio-fluorogenic co-polymerization' or RFCP for short. The method is illustrated by results on the in situ monitoring of the accumulated dose within the irradiation chamber of a cobalt-60 gamma-ray source using a small plastic capsule containing about 0.2 ml of an RFCP solution. Remote monitoring of the fluorescence is carried out on a timescale of seconds using optical fibres connecting the probe to a 360 nm LED excitation source and a miniature spectrophotometer. The fluorescence is permanent and the intensity is linearly proportional to the accumulated dose from a few tenths of a gray up to hundreds of gray. The sensitivity to dose depends on the polymerizable monomer used and obeys a square root dependence on dose rate over the range studied, 0.27–3.76 Gy min−1. The polymeric nature of the fluorescent product suggests that the RFCP effect could be used to provide fixed two- or three-dimensional fluorescent images of dose deposition in gel films or phantoms.
General scientific summary. Accurate knowledge of the radiation dose given during radiotherapy treatment procedures is essential. We have developed a dosimetric method that is based on a new principle: 'radio-fluorogenic co-polymerization' or RFCP. On exposure to high-energy radiation an initially non-fluorescent RFCP medium becomes fluorescent with an intensity proportional to the radiation dose. We show how a small volume (< 0.2 ml) of an RFCP solution can be used to monitor in situ and in real time the accumulated dose within a gamma-ray source with an accuracy better than 0.1 gray; considerably less than the fractionated dose of about 2 gray delivered during radiotherapy treatment. The fluorescent product formed in RFCP is a high molecular weight polymer. This opens up the possibility of using semi-rigid RFCP gels to produce 2D and 3D fluorescent images of the spatial dose distributions obtained with high-energy photon and particle beams used in modern radiotherapy.
For more information on this article see medicalphysicsweb.org87.55.N- Radiation monitoring, control, and safety
29.40.Cs Gas-filled counters: ionization chambers, proportional, and avalanche counters
Accelerators, beams and electromagnetism
Issue 10 (21 May 2009)
Received 10 February 2009, in final form 29 March 2009
Published 6 May 2009
J M Warman et al 2009 Phys. Med. Biol. 54 3185
Chunhua Men et al 2009 Phys. Med. Biol. 54 6565
Valery V Tuchin 2005 J. Phys. D: Appl. Phys. 38 2497
C A Perottoni and J A H da Jornada 2001 J. Phys.: Condens. Matter 13 5981
Xuejun Gu et al 2009 Phys. Med. Biol. 54 6287
Jeremy C Hebden et al 2002 Phys. Med. Biol. 47 4155
C Boudou et al 2007 Phys. Med. Biol. 52 4881
Q Jackie Wu et al 2008 Phys. Med. Biol. 53 673
E F Fincham 1925 Trans. Opt. Soc. 26 239
J Storrs Hall 1999 Nanotechnology 10 323